Improved film uniformity is important in plasma-enhanced chemical vapor deposition (PECVD) and plasma enhanced atomic layer deposition (ALD) technologies. The chamber systems implementing PECVD and ALD are associated with a hardware signature that contributes to nonuniform film deposition. For example, the hardware signature can be associated with chamber asymmetry and with pedestal asymmetry. Furthermore, many processes experience azimuthal nonuniformity of various origins. As customers push to locate die ever closer to the wafer edge, the numerical contribution of this azimuthal nonuniformity to overall nonuniformity grows. Despite best efforts to minimize damage and/or non-uniform deposition profiles, traditional PECVD and plasma ALD schemes still need improvement.
In particular, multi-station modules performing PECVD and ALD feature a large, open reactor that may contribute to azimuthal nonuniformities (e.g., NU in the theta direction). For example, some nonuniformities may result in a characteristic film thickness tilt towards the spindle transfer mechanism in the center of the reactor. Nonuniformities also exist in single station modules, due to nonuniform physical chamber geometries including those caused by assembly and component manufacturing tolerances.
Traditionally, deposition nonuniformities have been compensated by physically tilting the showerheads, such that the showerheads are intentionally oriented not parallel to the pedestals. Although not an elegant solution, it has been historically effective. However, the effectiveness of this scheme is growing ever more limited, especially as die size decreases and edges of the wafer are increasingly being sourced for dies.
Processing the wafer in multiple orientations without rotating the hardware signature has been shown to be effective in filtering out azimuthal non-uniformity. The most basic current method in the prior art includes partially processing the wafer, removing the wafer from the process chamber, rotating the wafer in a separate wafer handler, and then reinserting the wafer for further processing in the new orientation. The main advantage of this method is no hardware inside the chamber is rotated. However, this prior art solution has disadvantages of throughput, contamination, and significant extra hardware.
Another solution in the prior art rotates the whole pedestal during processing. However, this solution has the adverse property of rotating the non-uniformity associated with the pedestal along with the wafer. In that case, the pedestal can have a non-uniformity signature that may not be negated and may appear on the wafer during processing. Moreover, edge effects of the wafer in a pocket are another class of the non-uniformity that is directly rotated with the wafer when the whole pedestal is rotated during processing. That is, non-uniformity is not appreciably improved with pedestal rotation (e.g., in ALD oxide deposition). Furthermore, in addition to limited performance, rotating the whole pedestal requires the expense of passing RF power through the rotating pedestal. This requires a costly circuit for impedance matching through a slip ring to pass sufficient RF power to the plasma. Rotating the whole pedestal also complicates the delivery of fluids and gases, used for cooling for instance. Additionally, heating systems present in the pedestal also requires rotation, adding to cost and complexity.
It is in this context that disclosures arise.